The Tata group firm had briefly replaced RIL as the country's most-valued firm late last month, but could not hold on to the top ranking.
A sharp plunge in TCS shares had pushed the company to third position after RIL and ONGC earlier this month and a further retreat led to the country's largest software exporter slipping to fourth slot in the market valuation charts today.
At the end of today's trade, TCS had a market value of Rs 216,135.91 crore -- lower than RIL's 242,424.06 crore, ONGC's Rs 223,939.95 crore and CIL's Rs 221,893.88 crore.
Meanwhile, RIL regained its position as the most influential stock on the Sensex on the basis of weight in the stock market barometer index from another IT major, Infosys, in today's trade.
RIL now carries a Sensex weight of 9.78%, as against Infosys' 9.52%.
The Sensex weight of a stock is determined on the basis of its free-float market capitalisation, or the value of shares held by non-promoter shareholders that are freely available for trading.
ITC currently has the third highest weight on the Sensex after RIL and Infosys.
In terms of full market valuation, Infosys is ranked sixth after RIL, ONGC, Coal India, TCS and ITC.
RIL shares soared by 3.8% today, while Infosys gained 1%, but TCS lost 0.28% on a day when the Sensex gained 1.7%, or 276.69 points.
State-run CIL gained 3.2%, while ONGC also appreciated by 2.05%.